If you have hopes that you might make it to pitch in professional baseball, you may want to consider how much specialization has taken over the game of baseball with Starters, Middle-Inning Relievers, Set-Up Men, and Closers.
How long do you think it will be before we start hearing about a “7th inning Bridge” role?
"So, where do you think you fit into this developing hierarchy of roles for pitchers?"
While there are remarkable exceptions as starters, like Pedro Martinez [5’ 11’ 170 lbs], only two pitchers listed as 5-7 or shorter won as many as 100 games in the majors, Bobby Shantz, a 5-6 former Yankee, was 119-99 pitching from 1949-64, and the 5-7 Dolf Luque compiled a 194-179 mark with four teams from 1914 to 1935. Each had one 20-win season.
There are many reasons that today’s scouts are looking for potential starters to be tall and large; Pat Borzi of the NYT named two:
¶ Taller pitchers, with their longer arms and lengthier strides, actually release the baseball closer to home plate than shorter pitchers — thus further denying, perhaps by a fraction of a second or two, the batter the time he needs to react to any particular pitch.
¶ Taller pitchers, throwing off an elevated mound — as a function of torque or leverage or some combination of physical factors, including the ability to, as pitchers themselves say, get on top of their pitches — can simply be tougher to hit.
SABR’s Glen P. Greenberg’s study in Fall 2010 Baseball Research Journal, “Does a Pitcher’s Height Matter?” begs to differ:
“These data demonstrate that there is no statistical evidence that shorter pitchers are more or less durable than taller pitchers. The statistics suggest that they are just as prone to each type of injury, they recover at the same rate and they get injured as often. Given that durability is the most often cited concern for baseball executives when drafting shorter pitchers, the evidence in this study that durability does not correlate to a pitcher’s height is highly significant. Brad Steil explained the prevailing theory as ‘You know, a large, strong body is more durable in general.’
However, the data contradict that claim.” 
However, Mr. Greenberg admits there is a statistically significant difference that shows that shorter pitchers throw fewer innings, but he is willing to simply shrug it off:
“…the reason shorter pitchers throw fewer innings may be that they’re less durable or it may be that managers and baseball executives believe that shorter pitchers are less durable. Even if starting left-handed pitchers who are shorter are in fact less durable, the difference, while statistically significant, is still not that great.” 
Regardless of experts who conduct statistical analyses, today’s scouts and who may not subscribe to the SABR Research Journal, still tend to dismiss pitching prospects who will top out at less than 6-feet tall and less than 200 lbs, especially when looking at potential MLB starters.
When Tim Lincecum had phenomenal success with the Giants as a “small” starter at 5’ 11” and 170 lbs, many stories were written to say “Little Guys Can Be Starters.” The problem was that most pitching coaches said, from the time they first saw Lincecum’s body type and windup, which was full of extreme effort and put stress on his body, they predicted that he would not maintain his success as a starter.
Bleacher Report predicts he will be a bust for the Giants in the future:
“After winning two Cy Young Awards in 2008 and 2009, Lincecum posted a combined 4.76 ERA (versus a park-adjusted 72 ERA+), 1.38 WHIP and 2.31 strikeouts-per-walks ratio over the past two seasons.
No longer the ace he was once was, the Giants are essentially paying Lincecum for his once-promising pitching career—not for the pitcher he currently is and will continue to be.
While he may already be headed for the DL, he might resurrect his career by switching to a new role; he may have the stamina and stuff to become a closer, or he may be relegated to the “Middle Innings” relief group. It seems apparent that, in his case, the exertion and strength required to start is just not there.
Another example is of a short stature pitching prospect Toronto’s young starter Marcus Stroman.
“The 22nd overall pick in the 2012 draft, Stroman had the talent to go much higher than that. His electric stuff, highlighted by a plus-plus fastball-slider combination. He has been ratted as high as a No. 2 starter.
Stroman’s biggest knock, and why he doesn’t rate higher on prospect lists, is his small stature. He is listed at 5’9”, two inches shorter than Tim Lincecum.
You rarely see front-line starting pitchers under 6-feet tall because their frames can’t handle the workload, or a lack of height makes the fastball straighter and easier to elevate because there’s no downhill plane on it.”
[Bleacher Report: https://login.yahoo.com/config/login_verify2?]
Today it is not unusual to see pitchers designated as closers at the college level, and we may soon see it at the High School level as well, as it becomes clear that it is an identifiable career path to professional baseball. Certainly, many minor league affiliates are identifying pitchers as closers.
In May, 2013 the Los Angeles Times recognized College closers:
Sherfy, a junior, has 16 saves for Oregon and is 2-0 with a 1.09 ERA.
Berg, a sophomore, has 12 saves for UCLA and is 6-0 with an 0.68 ERA, including 25 2/3 consecutive scoreless innings.”
Besides the role of starter, middle-reliever, and closer, there is the role of “situational lefty,” A “situational lefty” who comes in to the game for a specific purpose—to get out a left-handed batter.
Typically, this occurs late in a game, when the opposing team has sent up a Left-handed pinch hitter and, whether he gets the batter out, or not, the “situational lefty” is done for the night and is promptly replaced by a RHP.
In the current hierarchy of pitching prospects we have the Starter, the Closer, the Situational Lefty, and the Middle Relief pitchers. When scouts at the H. S. or College level are evaluating young pitchers, they are primarily interested in finding starters, although they may start referring to some prospects as “closer” material.
Most amateur pitchers who will be drafted by MLB in the summer will be starters, because “Middle Relief” suggests pitchers who failed as starters, closers and situational Lefties.
By the time a pitching prospect reaches College level, he might want to evaluate his body type and the quality of his various pitches and then enhance his chances of advancing to professional baseball by establishing an identity for himself as a starter, closer, even a situational lefty.
With a “Quality Start” in MLB defined as pitching 6 or more innings, while allowing three or fewer runs, we may soon see a new specialty: The 6th Inning “Pre-Bridge reliever,” who will be followed by the “Bridge Reliever,” followed by the “Set-Up” pitcher and, finally, the closer.
And, any reliever who is dragged into a game during the first five innings may be called a “Pain Reliever.”
In another column, I will discuss the advantage of planning several starters, including lefties and knuckle-ballers, for every game.